Derealization is an alteration in the perception of the external world, causing those with the condition to perceive it as unreal, distant, distorted or falsified. Other symptoms include feeling as if one's environment is lacking in spontaneity, emotional coloring, and depth. It is a dissociative symptom that may appear in moments of severe stress.
Derealization is a subjective experience pertaining to a person's perception of the outside world, while depersonalization is a related symptom characterized by dissociation towards one's own body and mental processes. The two are commonly experienced in conjunction with one another, but are also known to occur independently.
Chronic derealization is fairly rare, and may be caused by occipital–temporal dysfunction. Experiencing derealization for long periods of time or having recurring episodes can be indicative of many psychological disorders, and can cause significant distress. However, temporary derealization symptoms are commonly experienced by the general population a few times throughout their lives, with a lifetime prevalence of up to 26–74% and a prevalence of 31–66% at the time of a traumatic event.
The experience of derealization can be described as an immaterial substance that separates a person from the outside world, such as a sensory fog, pane of glass, or veil. Individuals may report that what they see lacks vividness and emotional coloring. Emotional response to visual recognition of loved ones may be significantly reduced. Feelings of déjà vu or jamais vu are common. Familiar places may look alien, bizarre, and surreal. One may not even be sure whether what one perceives is in fact reality or not. The world as perceived by the individual may feel as if it were going through a dolly zoom effect. Such perceptual abnormalities may also extend to the senses of hearing, taste, and smell.
The degree of familiarity one has with their surroundings is among one's sensory and psychological identity, memory foundation and history when experiencing a place.